1. Technical Field
The embodiments herein generally relate to medical devices, and, more particularly, to an anti back-out mechanism used during orthopedic surgeries.
2. Description of the Related Art
Cervical spinal fusion surgeries are often carried out to eliminate motion at a vertebral segment. These fusions may also prevent the spine from falling into a collapsed deformity (e.g., kyphosis). Incisions are made in the front of the neck in anterior cervical fusions. These fusions remove pressure from the nerve roots caused by bone spurs or a herniated disc. Anterior cervical spinal fusion surgeries are commonly performed in conjunction with anterior cervical discectomy (e.g., removing the disc). In addition, anterior cervical spinal fusions are carried out to treat cervical instability due to trauma (fractures or dislocations), tumor, and infections, etc.
It is also necessary to secure and stabilize the cervical vertebrae during spinal fusion surgeries. Stabilization leads to an appropriate healing or a preferred result. To accomplish this, a cervical plate is mounted on one or more vertebrae during the surgery. The plates should be firmly secured to the spinal column so that the plates are not tattered out when they are stressed and they should be capable of placement and fixation in a manner that is convenient for the surgeon. Typically, screws are used to mount the cervical plate to the one or more vertebrae. It is important to properly align the plate on the vertebrae for receipt of mounting screws during a mounting process.
The interface between the screws and the bone presents some problems of stability. Due to anatomical forces on the skeleton the screws securing the plate to the cervical spine loosen over time resulting in movement of the screw, and back out of the plate or bones. This is usually termed as “back-out”, and it can lead to increased pain, infection, and/or possible death of the patient.
Conventional devices typically do not inhibit backing out of the bone screws. Threaded screws with heads that engage threads in the cervical plate to lock the screws in the plate are available. However, these systems generally do not provide adequate locking of the screw to the plates, leading to loosening of screws over time. Most cervical plates incorporate a built-in expanding ring that expands to allow a bone screw to go through, and collapse after passing the screw through the ring to prevent the screw from backing out over time. In these designs, particularly as the rings are small in size, it generally cannot be detected whether the rings have secured the screw. Further, adjustments in the fitting of the cervical plate typically cannot be made due to poor visibility and control. Accordingly, there remains a need for a new orthopedic anti-back out mechanism to secure and stabilize the vertebral column.